from multiprocessing import Pool
import os
import time
import random


def long_time_task(name):
    print('Run task %s (%s)' % (name, os.getpid()))
    start = time.time()
    time.sleep(random.random() * 3)
    end = time.time()
    print('Task %s runs %0.2f seconds.' %(name, (end-start)))

if __name__ == '__main__':
    print('Parent process %s.' % os.getpid())
    p = Pool(4)
    for i in range(5):
        p.apply_async(long_time_task, args=(i,))
    print('Waiting for all subprocess done...')
    p.close()
    p.join()
    print('All subprocess done.')